<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    function aa(a, i) {
      let x = a % i
      a = i
      i = x
      if (x == 0) {
        return a
      }
      else {
        aa()
      }
    }
    console.log(aa(18, 3));

  </script>
</body>

</html>